Gun barrel with variable capacity chamber



Dec. 26, 1967 H, GROSSCHOPF ET AL. 3,359,856l

GUN BARREL WITH VARIABLE CAPACITY CHAMBER Filed May 5, 1966 United States Patent O s claims. (cl. 89-16) ABSTRACT OF THE DISCLOSURE A gun barrel having an outer supporting barrel member and a bore tube within the barrel member longitudinally disp-laceable with relative movement between the barrel member and t-he bore tube. Means are provided mounted on the gun to adjust the barrel member and bore tube relative to each other, and the bore tube has a tapering bore portion at the inner end thereof.

The invention relates to gun barrels which consist of an outer barrel as supporting member and a bore tube exchangeably arranged in the outer barrel.

The difference between a gun and a howitzer is Well known. Because of the dilfering effects and applications yguns and howitzers have, in particular, different barrel lengths. Thus, a gun has a much longer barrel than a howitzer giving a greater muzzle velocity and thus a very flat trajectory and a long range. Howitzers have shorter barrels, a medium muzzle velocity, a very sharp trajectory and a shorter range. Howitzers are, therefore, particularly suitable for attacking targets behind cover and at short range.

The difference between guns and howitzers is reected in the propelling charges found in shells for these guns. With the same shell (i.e. of the same shape and weight) a larger propelling charge is required for the high performance gun that for the lower performance howitzer. There is therefore a difference in the dimensions of the weapon chamber, which is longer in guns than in howitzers.

If a gun designed for long-range firing is now required to be used to attack closer and possibly concealed targets, difficulties arise in that the large cubic capacity chamber does not allow perfect combustion of the smaller propelling charge of the howitzer shell which has to be used. Uncontrollable combustion processes occur which make it impossible to establish a ring table, so that an effective attack on the target is difficult to realize.

According to the present invention, a barrel with a variable capacity chamber is created. The cubic capacity can be adapted t the size of the propelling charge of the round to be red. This makes it possible to re according to a ring table at all ranges.

A barrel embodying the invention consists of an outer barrel member as supporting member and a bore tube so arranged in the outer barrel so that the bore tube is longitudinally displaceable with respect to the outer barrel member and capable of being xed in position, in such a way that the cubic capacity of the chamber can be altered by longitudinal displacement of the bore tube.

In a preferred embodiment of the invention the rear end of the bore tube projecting into the chamber has a bore expanding from the internal diameter or calibre of the bore tube almost to the outside diameter of the tube and `forms a variable section of the chamber.

The axial displacement of the bore tube can be eifected in various ways. For this purpose the bore tube is pref- ICC ferably provided over part of its length with an external thread and is guided in a threaded nut rotatably supported in the outer barrel member. By rotation of the nut, which can be eiected, for example, by means of a crank by way of a worm gear, the bore tube is displaced longitudinally, in such manner that the chamber is altered in length and thus in cubic capacity.

Other methods of adjustment can be employed, for example, the bore tube may be |movable by hydraulic means. In this case the bore tube can be provided on its periphery with an annular piston, to either side of which pressure can be applied in a cylinder chamber provided in the outer barrel. The cylinder chamber may take the form of a cylindrically-widened section yon the outer barrel.

By way of example only, an embodiment of the invention will now be described in greater detail with reference to the accompanying drawings of which:

FIG. 1 is a vertical longitudinal section through the gun:

FIG. 2 is a horizontal longitudinal section taken on line II-II of FIG. 1 in the direction of the arrows, and,

FIG. 3 is a top view partly in section looking in the direction of arrow III, FIG. 1, of part of the gun.

The barrel consists of an outer barrel member 1 as supporting member and a bore tube 2 arranged in the latter so that it is longitudinally displaceable with respect to the outer barrel. The outer barrel member 1 is connected by means of the screw joint 3 to a breech section 4. Over the greater part of its length, the outer barrel member 1 has a cylindrical bore 5 in which the bore tube 2 is supported and guided. A further support is provided by a guide bearing 6 which is attached to the front end of the outer barrel member 1. In the region between the cylindrical bore 5 and the guide bearing 6, the outer barrel has two sections 7 and 8 of enlarged diameter and of which the widened section 8 serves to support a threaded nut 9. Engaged with the threaded nut is a thread 10 -on the external surface of the boretube in the region of section 7. By rotation of the threaded nut, the bore tube 2 is longitudinally displaced with respect to the outer barrel. For this purpose, the threaded nut has on its periphery a toothed section 13 in which is engaged a pinion 14 supported on the outside of the outer barrel. The pinion is driven by a crank drive 15 via a universal joint 16. The crank drive 15 is mounted upon the breech section 4.

The rear end of the bore tube projecting into the chamber 11 has a tapered bore portion 12 which expands from the internal diameter or calibre of the bore tube approximately to the outside diameter of the latter and defines the chamber at the front. In that way there is formed a chamber which is variable in length and thus in cubic capacity.

In the drawing, the barrel is shown with asmall chamber, as is suitable for the smaller propellent charge of a howitzer shell. The bore tube is shown at the limit of its movement to the left as seen in FIG. 1. On rotation of the annular nut by turning the crank drive 15, the bore tube is displaced in a longitudinal direction to the right, whereby the chamber is enlarged until it has the cubic capacity required for the prescribed range and corresponding to a larger propelling charge of a gun shell.

The cubic capacity of the chamber set in each case can be indicated by means of markings provided either on the front section of the bore tube projecting out of the outer barrel or on the crank drive.

By means of the tapered bore 12 increasing as described from the inside to the outside diameter of the bore tube, a tube wall is produced which tapers constantly towards the rear end of the bore tube and the outer end 3 of which ts against the wall of the outer barrel, under the gas pressure, in the manner 0f a packing ring.

We claim:

1. A gun barrel comprising in combination an outer supporting barrel member, a bore tube positioned in the barrel member and longitudinally displaceable relatively thereto in such manner as to vary the capacity of the chamber of the weapon, and means for adjustably holding the boretube in a required position in the barrel member, said bore tube having an end inside said barrel member and a tapering bore portion at said end, said taper bore increasing in size from the internal diameter of said bore tube to substantially the external diameter of the latter and forming a variable position part of said chamber.

2. A gun barrel as claimed in claim 1 and further comprising an external screw thread over part of the length of said bore tube, a threaded member engaged on said external screw thread and means for rotatably supporting said threaded member on said barrel member.

3. A gun barrel as claimed in lclaim 1 and further comprising an external screw thread over part of the length of said bore tube, a threaded member engaged References Cited UNITED STATES PATENTS 121,455 12/ 1871 Fitzgerald 89--16 834,341 10/1906 Tucker 4277 1,480,957 1/1924 Schneider 89-1 FOREIGN PATENTS 73 9,776 1/1933 France.

OTHER REFERENCES Army Unveils Atomic Artillery, Popular Mechanics, November 1952, pp. 123-5.

BENIAMIN A. BORCHELT, Primary Examiner.

S. C. BENTLEY, Assistant Examiner. 

1. A GUN BARREL COMPRISING IN COMBINATION AN OUTER SUPPORTING BARREL MEMBER, A BORE TUBE POSITIONED IN THE BARREL MEMBER AND LONGITUDINALLY DISPLACEABLE RELATIVELY THERETO IN SUCH MANNER AS TO VARY THE CAPACITY OF THE CHAMBER OF THE WEAPONS, AND MEANS FOR ADJUSTABLY HOLDING THE BORETUBE IN A REQUIRED POSITION IN THE BARREL MEMBER, SAID BORE TUBE HAVING AN END INSIDE SAID BARREL MEMBER AND A TAPERING BORE PORTION AT SAID END, SAID TAPER BORE INCREASING IN SIZE FROM THE INTERNAL DIAMETER OF SAID BORE TUBE TO SUBSTANTIALLY THE EXTERNAL DIAMETER OF THE LATTER AND FORMING A VARIABLE POSITION PAR TOF SAID CHAMBER. 